Cluster DIAGNOSTIC MORPHOLOGY Adults: • Adults are 3/8 inch long (8 mm) and slightly larger than the house fly. • Dark grey non-metallic thorax lacking distinct stripes but with numerous, short, golden hairs which may be lost in older specimens. • Dorsum of thorax has three diffuse, longitudinal, black bars that are not conspicuous. • Veins in wings are bent forward near the tips. • The wing tips overlap when in rest.

GENERAL INFORMATION Immature Stage: The is widely distributed throughout • Larvae have soft, maggot-like bodies, and are whitish in color. , Canada, and the United States excepting • Larvae are rarely seen because their instar life stages are spent as a parasitoid to the states that border on the Gulf of Mexico. The hosts, emerging as adult . name reflects the species’ habit of forming compact clusters of hibernating adult flies. Cluster flies typically live outdoors and enter FOOD SOURCES structure to overwinter, they are best removed structures seeking harbourage to overwinter in the Adult cluster flies do not pose substantial risks to through HEPA vacuuming as their defecations and fall, and they often aggregate in secluded and cultural heritage collections because their food their crushed corpses can leave stains. It also is sometimes inaccessible spaces, such as wall sources are found outdoors including ripe fruits highly advisable to HEPA vacuum their dead cavities, attics, and false ceilings where they are and the nectar of flowers. Moreover, cluster flies bodies as they can serve as a food sources for known to seek out the warmest areas. Typically, are not believed to be a health hazard to humans Dermestid . Moreover, the use of chemical cluster flies attempt to invade the same structure because they are not attracted to human foods. treatments to kill cluster fly infestations inside of year after year; however, they do not reproduce are the sole food source of cluster fly wall voids that are inaccessible to HEPA within these structures. Their presence within a larvae (maggots). vacuuming is highly discouraged. structure indicates mechanical failures in protecting the building’s envelope. The best LIFE CYCLE method to prevent and control cluster flies is to Cluster flies hatch from and pupate outdoors. exclude them from entering the structure. While Their life cycle begins when female cluster flies cluster flies do not pose significant threats to lay their eggs loosely on damp soil and in loam. cultural heritage collections, their defecations can After about a week, the larvae hatch, and after stain interior décor and decorative arts, and their about another week the larvae seek out and corpses can become food for other types of pests parasitically invade an earthworm host particularly Dermestid beetles. () which serves as its food source. Once they become fully grown, cluster flies bore SIGNS OF INFESTATION there way out of their hosts, and then pupate into Small clusters of mature flies are typically an adult flies in the soil. Depending on weather encountered in structures during the fall, when conditions, two generations are normal but up to they enter to hibernate, and also during the spring, four are possible. Adult cluster flies enter when they attempt to leave the structure. buildings in search of harbourage in order to Unfortunately, once cluster flies have entered a overwinter during the fall. structure to overwinter, they can be very difficult to locate and control. Hibernating individuals can CONTROL & TREATMENT be stimulated into activity by warmth such as by Cluster fly infestations indicate failures in the activation of a furnace. Once stimulated, protecting the building’s envelope as they gain cluster flies will seek light, and they are often access from the exterior through small gaps and found climbing on windows and panes. voids. Typically, they tend to cluster on the exterior of a building in large numbers prior to crawling into the harbourages. Pest management strategies stress prevention and the use of mechanical and physical barriers to close and seal potential access points. Although total exclusion may not be achievable (especially in historic properties), best practices ought to include filling cracks and other potential access points with wire mesh. Once cluster flies have entered a

Information current as of 20 March 2015. For more information visit www.museumpests.net.

Fact Sheet: Cigarette

Photo credit: Malcolm Storey, Male - dorsal view - close-up - highly enlarged - white background, Encyclopedia of Life: http://eol.org/data_objects/27020433.

Photo credit: Malcolm Storey, Female - lateral and dorsal views, Encyclopedia of Life: http://media.eol.org/content/2012/12/05/10/91744_orig.jpg.

Sources: Hedges, ed at al, Mallis: Handbook of Pest Control, 10th Edition (2012): 1015-1019. Smith and Whitman, NPCA Field Guide to Structural Pests (1992): 6.2.1.

Information current as of 2 March, 2012 For more information visit www.museumpests.net Page 2